Field of Endeavor
The present application relates to spectroscopy and more particularly to cavity ring down spectroscopy.
State of Technology
This section provides background information related to the present disclosure which is not necessarily prior art.
Biological AMS is a technique in which carbon-14 is used as a tag to study, with extreme precision and sensitivity, complex biological processes, such as cancer, molecular damage, drug and toxin behavior, nutrition and other areas. When biological accelerator mass spectrometry (AMS) was first developed the process of preparing the samples was time-consuming and cumbersome. Physicists and biomedical researchers used torches, vacuum lines, special chemistries and high degrees of skill to convert biological samples into graphite targets that could then be run through the AMS system. At that time, it took two days of work to prepare only eight samples. Additional information about Accelerator Mass Spectrometry is contained in the article: “A New World of Biomedical Research: The Center for Accelerator Mass Spectrometry,” Science & Technology Review, November 1997, pp. 6-11, a portion of which is reproduced below.
Mass spectrometry has been used since early in this century to study the chemical makeup of substances. A sample of a substance is put into a mass spectrometer, which ionizes it and looks at the motion of the ions in an electromagnetic field to sort them by their mass-to-charge ratios. The basic principle is that isotopes of different masses move differently in a given electromagnetic field.An accelerator was first used as a mass spectrometer in 1939 by Luis Alvarez and Robert Cornog of the University of California at Berkeley. To answer what at the time was a knotty nuclear physics question, they used a cyclotron to demonstrate that helium-3 was stable and was not hydrogen-3 (tritium), which is not stable. Accelerators continued to be used for nuclear physics, but it was not until the mid-1970s that they began to be used for mass spectrometry. The impetus then was to improve and expand radiocarbon dating. Van de Graaff accelerators were used to count carbon-14 (14C) for archaeologic and geologic dating studies.Accelerator mass spectrometry (AMS) quickly became the preferred method for radiocarbon dating because it was so much quicker than the traditional method of scintillation counting, which counts the number of 14C atoms that decay over time. The half-life of 14C is short enough (5,730 years) that counting decayed atoms is feasible, but it is time-consuming and requires a relatively large sample. Other radioactive isotopes have half-lives as long as 16 million years and thus have such slow decay rates that huge samples and impossibly long counting times are required. The high sensitivity of AMS meant that these rare isotopes could be measured for the first time.Before a sample ever reaches the AMS unit, it must be reduced to a solid form that is thermally and electrically conductive. All samples are carefully prepared to avoid contamination. They are reduced to a homogeneous state from which the final sample material is prepared. Carbon samples, for instance, are reduced to graphite. Usually just a milligram of material is needed for analysis. If the sample is too small, bulking agents are carefully measured and added to the sample.
The article: “A New World of Biomedical Research: The Center for Accelerator Mass Spectrometry,” Science & Technology Review, November 1997, pp. 6-11, is incorporated herein in its entirety by this reference.
Additional information about accelerator mass spectrometry is contained in the article: “A New Accelerator Mass Spectrometry System for 14C quantification of Biochemical Samples,” by Ted J. Ognibene, Graham Bench, Tom A. Brown, Graham F. Peaslee, and John S. Vogel, in International Journal of Mass Spectrometry 218 (2002) 255-264, a portion of which is reproduced below.
Accelerator mass spectrometry (AMS) provides carbon isotope ratio quantification at part per quadrillion sensitivity in milligram-sized samples with part per thousand precision. AMS was originally developed for use in the geosciences and archeology as a means to determine radiocarbon ages. AMS has been used in the biosciences to provide highly sensitive 14C quantification at environmentally relevant doses. Recent conference proceedings highlight experiments using 14C, as well as other isotopes of biological significance. However, 14C remains one of the most widely used tracers in biochemical studies of toxicology, nutrition, carcinogenesis, pharmacokinetics and protein quantification.
The article: “A New Accelerator Mass Spectrometry System for 14C-quantification of Biochemical Samples,” by Ted J. Ognibene, Graham Bench, Tom A. Brown, Graham F. Peaslee, and John S. Vogel, in International Journal of Mass Spectrometry 218 (2002) 255-264, is incorporated herein in its entirety by this reference.